linux-kernel - Re: [PATCH] x86/speculation/spectre_v2: Exclude Zhaoxin CPUs from SPECTRE

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Message-ID: <87r1zzuy48.fsf@nanos.tec.linutronix.de>
Date:   Thu, 16 Jan 2020 18:09:27 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tony W Wang-oc <TonyWWang-oc@...oxin.com>, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org, luto@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, peterz@...radead.org,
        fenghua.yu@...el.com, vineela.tummalapalli@...el.com,
        linux-kernel@...r.kernel.org
Cc:     DavidWang@...oxin.com, CooperYan@...oxin.com,
        QiyuanWang@...oxin.com, HerryYang@...oxin.com
Subject: Re: [PATCH] x86/speculation/spectre_v2: Exclude Zhaoxin CPUs from SPECTRE_V2

Tony,

Tony W Wang-oc <TonyWWang-oc@...oxin.com> writes:

> @@ -1023,6 +1023,7 @@ static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
>  #define MSBDS_ONLY		BIT(5)
>  #define NO_SWAPGS		BIT(6)
>  #define NO_ITLB_MULTIHIT	BIT(7)
> +#define NO_SPECTRE_V2		BIT(8)
>  
>  #define VULNWL(_vendor, _family, _model, _whitelist)	\
>  	{ X86_VENDOR_##_vendor, _family, _model, X86_FEATURE_ANY, _whitelist }
> @@ -1084,6 +1085,10 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
>  	/* FAMILY_ANY must be last, otherwise 0x0f - 0x12 matches won't work */
>  	VULNWL_AMD(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
>  	VULNWL_HYGON(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
> +
> +	/* Zhaoxin Family 7 */
> +	VULNWL(CENTAUR,	7, X86_MODEL_ANY,	NO_SPECTRE_V2),
> +	VULNWL(ZHAOXIN,	7, X86_MODEL_ANY,	NO_SPECTRE_V2),
>  	{}
>  };
>  
> @@ -1116,7 +1121,9 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
>  		return;
>  
>  	setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
> -	setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
> +
> +	if (!cpu_matches(NO_SPECTRE_V2))
> +		setup_force_cpu_bug(X86_BUG_SPECTRE_V2);

That's way better. But as you might have noticed yourself this conflicts
with the other patch which excludes these machines from the SWAPGS bug.

Granted it's a trivial conflict, but maintainers are not there to mop up
the mess others create. So the right thing here is to resend both
patches as a patch series with the conflict properly resolved.

Thanks,

        tglx